Question: Is there a search engine that can handle cross-domain search and provide results from multiple sites and sub-domains?

If you need a search engine that spans multiple domains and can return results from multiple sites and sub-domains, SearchIQ is another top contender. It has cross-site search technology along with A.I. based search logic, customizable result ranking and a fast CDN. It also has plugins for WordPress and other software that makes it a good fit for content networks, companies and other organizations.

Another good option is Algolia, which offers an AI-powered search foundation geared for businesses and developers. It offers fast, scalable and personalized search experiences with integration that takes minutes. Algolia serves a variety of industries and use cases, including enterprise search, headless commerce and voice search, and has flexible pricing and a $10,000 credit limit for startups.

Vespa is also worth a look, since it combines vector, lexical and structured data search into one unified service. It can handle large-scale and efficient machine-learned model inference and can be integrated with a variety of machine learning tools. That makes it a good fit for building high-performance and highly scalable search applications that can handle a variety of data types and sources.

If you want an open-source option, OpenSearch is a flexible and scalable search engine that supports geospatial indexing, alerting, SQL/PPL support and anomaly detection. Because it can run on different infrastructure and support high availability and multicloud environments, OpenSearch is a good choice for building your own customizable search solutions for document indexes and e-commerce sites.